Klein is 1-0 with a 1.69 ERA (3 ER/16.0 IP) in 6 games, including 2 starts with Round Rock. His last 2 outings have been as a starter with a 1.08 ERA (1 ER/8.1 IP) in games at Omaha on May 6 (1 ER/4.0 IP) and at Nashville on May 11 (0 ER/4.1 IP).
The right-hander opened the season with Texas with a 7.71 ERA (4 ER/4.2 IP) in 6 relief appearances before he was optioned to Round Rock on April 14. Klein made his major league debut with the Rangers in 2014, going 1-2, 2.84 (6 ER/19.0 IP) in 17 relief appearances.
Peguero is batting .186 with 4 homers and 9 RBI in 30 games for Texas since he was purchased from Round Rock on April 11. Texas has 10 days to trade, release, or outright Peguero to the minor leagues.
The team also announced that right-handed pitcher Stolmy Pimentel has cleared waivers and been assigned outright to Round Rock. Pimentel was designated for assignment on May 13 after going 0-1, 3.97 in 8 relief outings. He had been claimed on waivers from Pittsburgh on April 11.
With today's moves, the Rangers have 39 players on their major league roster.